1. Department of Veterinary Microbiology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
2. Department of Veterinary Medicine, National Chung Hsing University, 250, Kwo-Kwang Rd., Taichung 40227, Taiwan, ROC.
3. Taiwan Provincial Research Institute for Animal Health, 376, Chung-Cheng Rd., Tam-Sui, Taipei, Taiwan, ROC.
4. Department of Veterinary Medicine, National Taiwan University, 142, Zou-Shan Rd., Taipei, Taiwan, ROC